HIV infection is a chronic process, taking about 2-10 years to develop from HIV-1 infection to the AIDS stage, and longer to develop the AIDS stage after HIV-2 infection. The entire course of the disease is currently divided clinically into three simple phases: 1. the acute phase of HIV-1 infection; 2. the asymptomatic HIV infection phase; and 3. the acquired immunodeficiency syndrome (AIDS) phase.